There are two elements in road traffic accident scene graph, base map and other elements in the site of traffic accident. The base map mainly includes traffic sings and traffic markings. Drawing traffic accident scene graph is a necessary link during disposing road traffic accident, while drawing the base map costs most of the time of drawing traffic accident scene. In order to save processing time of dealing with the traffic accident, the concept of road base map is proposed. The symbol design and data organization of the base map are analyzed. All this provides a new way to make the traffic accident scene graph.